The invention relates, on the one hand, to a method for filtering a suspension which is initially inducted through a filling shoe into a filter chamber on a cake side of a filter cloth, permeates the filter cloth to a filtrate side of the filter cloth, and flows from the filter chamber on the filtrate side in a filtered state as a filtrate, while a solid content of the suspension is deposited on the filter cloth as a filter cake, wherein the filter chamber in a closed state of a filter device is configured between a filter plate and a counter plate, and the filling shoe is anchored in the filter plate, and clamps the filter cloth with the filter plate in a sealing manner in the closed state, and wherein the filter device is subsequently opened, so that the filter plate and the counter plate have an offset and the filter cake is removed. Furthermore the invention relates to a filter device including at least one filter chamber, which is configured between a filter plate and a counter plate when the filter device is closed, into which filter chamber a suspension can be inducted on a cake side of a filter cloth through at least one filling shoe anchored in the filter plate and clamping the filter cloth with the filter plate in a sealing manner, and the suspension can permeate the filter cloth to the filtrate side thereof, wherein a solid content of the suspension can be deposited on the filter cloth as a filter cake, and the filter plate and the counter plate are at an offset from each other when the filter device is open, and the filter cake can be removed from the at least one filter chamber.
Filter devices with a plurality of filter plates as plate stacks and filter chambers, which are respectively configured between a filter plate and a second filter plate (as a counter plate), lying in parallel on the first filter plate or standing adjacent to it, are generally known e.g. from DE 199 56 617 A1. In the filter chambers, substantially in the respective separation plane between the filter plate and the associated counter plate, one or two filter cloths and a rubber elastic membrane are disposed depending on the configuration of the filter device. Subsequently, only the filter cloth is designated as filter cloth, which is clamped tight between a filter plate and a filling shoe anchored in the filter plate in a closed state of the filter device.
During filtering operation of the known filter devices, the filter chambers are supplied through the filling shoes with a pressurized suspension, which is to be filtered, and the suspension is pressed through the filter cloths. Thus, the solid content of the suspension is deposited on the filter cloth as a filter cake. The filtered suspension from which the solid content is purged flows out from the filter chambers as a filtrate below the filter cloth substantially without pressure.
After the filtration is completed, washing and pressing the filter cake, the filter chambers are opened one after the other by moving the respective filter plate and the associated counter plate away from one another to form an offset distance. In the open state, the filter cake is either removed respectively self-acting or with mechanical devices after the filtration is completed. When the filtering properties of the filter cloths are not sufficient anymore, the filling shoes inserted into the filter plates respectively through respective recesses of the filter cloths are manually disassembled, the filter cloths are removed from the filter chambers for removing the filter cake, the filter cake is removed from the filter cloths, and the filter cloths are cleaned or replaced as required and mounted again in the filter plates for reuse with the filter shoes.
Besides the substantial manual complexity of mounting and dismounting the filter cloths, and the filling shoes anchored through clamping in the filter plates, which hinders a partial automation of the process cycle, also the service life of the filter cloths in the known filter devices is very limited. Through the high pressure loading, and depending on the method, occasional substantial temperature loading, the filter cloths extend during operation, so that the recesses provided for the filling shoes with respective seal rings do not coincide with the geometry of the filter plates after few process cycles. During filtering operation, these recesses either are not disposed exactly over the anchoring locations of the filling shoes or the filter cloth develops wrinkles between the anchoring locations. Both lead to respective leakages at the particular locations of the known filter devices, and otherwise lead to increased mechanical loading and early failure of the filter cloths.
DE 103 03 817 A1 discloses such a method in which the filling shoe is pressed out by its own weight and by the weight of the membrane, when the filter device is opened.